Biphenyl

92-52-4

Hazard Summary-Created in April 1992; Revised in January 2000

Biphenyl is used in organic syntheses, heat transfer fluids, dye carriers,
food preservatives, as an intermediate for polychlorinated biphenyls,
and as a fungistat in the packaging of citrus fruits. In workers,
acute (short-term) exposure to high levels of biphenyl has been observed
to cause eye and skin irritation and toxic effects on the liver, kidneys,
and central and peripheral nervous systems. Kidney effects have
been observed in chronically (long-term) exposed animals. EPA has
classified biphenyl as a Group D, not classifiable as to human carcinogenicity.

Uses

Biphenyl is used in organic syntheses, heat transfer fluids, dye
carriers, food preservatives, as an intermediate for polychlorinated
biphenyls, and as a fungistat in the packaging of citrus fruits. (1,2,5,7)

Sources and Potential Exposure

Paper impregnated with biphenyl is used in citrus packing to reduce
fruit damage by fungus during shipment and storage. Biphenyl residue
on citrus fruits has been detected and individuals may be exposed by
ingestion of contaminated fruit. (2)

Biphenyl has been detected in drinking water. Individuals may
be exposed by the consumption of contaminated water. (2)

Assessing Personal Exposure

No information was located regarding the measurement of personal
exposure to biphenyl.

Health Hazard Information

Acute Effects:

In workers, acute exposure to high levels of biphenyl has been observed
to cause eye and skin irritation and toxic effects on the liver, kidneys,
and central and peripheral nervous systems. Symptoms include headache,
gastrointestinal pain, nausea, indigestion, numbness and aching of limbs,
and general fatigue. (1,2)

Tests involving acute exposure of rats, mice, and rabbits have demonstrated
biphenyl to have moderate acute toxicity
by ingestion and low to moderate
acute toxicity by dermal exposure. (3)

Chronic Effects (Noncancer):

In humans, chronic exposure is characterized mostly by central nervous
system symptoms, such as fatigue, headache, tremor, insomnia, sensory
impairment, and mood changes; however, such symptoms are rare. (1)

The primary effect seen in animal studies has been kidney effects,
which have been observed in rats chronically exposed to biphenyl by
ingestion. (2,4)

EPA has not established a Reference Concentration (RfC)
for biphenyl. (4)

The Reference Dose (RfD)
for biphenyl is 0.05 milligrams per kilogram body weight per day (mg/kg/d)
based on kidney damage in rats. The RfD
is an estimate (with uncertainty spanning perhaps an order of magnitude)
of a daily oral exposure to the human population (including sensitive
subgroups) that is likely to be without appreciable risk of deleterious
noncancer effects during a lifetime. It is not a direct estimator
of risk but rather a reference point to gauge the potential effects.
At exposures increasingly greater than the RfD,
the potential for adverse health effects increases. Lifetime exposure
above the RfD does not imply
that an adverse health effect would necessarily occur. (4)

EPA has high confidence in the principal study on which the RfD
was based because it was a well-conducted chronic bioassay covering
a wide dose range with an adequate number of both animal and toxicity
parameters assessed; low confidence in the database because the only
supporting data are unpublished; and, consequently, medium confidence
in the RfD. (4)

Reproductive/Developmental Effects:

No information is available on the reproductive or developmental
effects of biphenyl in humans.

Some evidence (not significant) of fetotoxicity has been observed
in rats exposed to high levels of biphenyl via gavage (experimentally
placing the chemical in the stomach). (2,4)

Cancer Risk:

No data on the carcinogenic effects of biphenyl in humans are available.
(4)

EPA considers available studies on carcinogenicity in mice and rats
to be inadequate. One study of mice orally exposed to biphenyl did not
result in any increased incidence of tumors. A second study found tumors
in treated and control rats, but their occurrence was not thought to
be related to biphenyl administration. (2,4)

EPA has classified biphenyl as a Group D, not classifiable as to
human carcinogenicity. (4)

Physical Properties

The chemical formula for biphenyl is (C6H5)2,
and it has a molecular weight of 154.20 g/mol. (5)

Biphenyl occurs as colorless leaflets that are insoluble in water.
(5)

Biphenyl has a pleasant, peculiar odor, with an odor threshold of
0.00083 parts per million (ppm) (0.005 milligrams per cubic meter (mg/m3).
(6,7)

The vapor pressure of biphenyl is 0.01 mm Hg at 25 °C, and it
has a log octanol/water partition coefficient (log Kow) of
3.16 to 4.16. (2)

Health Data from Inhalation Exposure

ACGIH TLV--American Conference of Governmental and Industrial
Hygienists' threshold limit value expressed as a time-weighted average;
the concentration of a substance to which most workers can be exposed
without adverse effects. NIOSH IDLH--National Institute of Occupational Safety and Health's
immediately dangerous to life or health concentration; NIOSH recommended
exposure limit to ensure that a worker can escape from an exposure condition
that is likely to cause death or immediate or delayed permanent adverse
health effects or prevent escape from the environment. NIOSH REL--NIOSH's recommended exposure limit; NIOSH-recommended
exposure limit for an 8- or 10-h time-weighted-average exposure and/or
ceiling. OSHA PEL--Occupational Safety and Health Administration's permissible
exposure limit expressed as a time-weighted average; the concentration
of a substance to which most workers can be exposed without adverse effect
averaged over a normal 8-h workday or a 40-h workweek.

The health and regulatory values cited in this factsheet were obtained
in December 1999.aHealth numbers are toxicological numbers
from animal testing or risk assessment values developed by EPA. bRegulatory numbers are values that have been
incorporated in Government regulations, while advisory numbers are nonregulatory
values provided by the Government or other groups as advice. OSHA
numbers are regulatory, whereas NIOSH and ACGIH numbers are advisory.

J.E. Amoore and E. Hautala. Odor as an aid to
chemical safety: Odor thresholds compared with threshold limit values
and volatilities for 214 industrial chemicals in air and water dilution.
Journal of Applied Toxicology, 3(6):272-290. 1983.

National Institute for Occupational Safety and
Health (NIOSH). Pocket
Guide to Chemical Hazards. U.S. Department of Health and Human
Services, Public Health Service, Centers for Disease Control and Prevention.
Cincinnati, OH. 1997.